Recently, hydrogen, which generates only water in combustion, is attracting attention as a clean energy medium from the viewpoint of preservation of the global environment and more recently as a fuel for fuel cell. Various methods of producing hydrogen as a fuel are known, and one of them is a method of producing hydrogen in a methanol-reforming reaction. Although methanol may be used as it is as a biomass fuel or the like, methanol as a source of hydrogen by reforming is attracting attention from the viewpoint of energy efficiency.
The reaction of producing hydrogen by reforming methanol is endothermic, and, for example in a methanol-reforming gas engine of fuel cell-powered vehicles, exhaust heat is used for raising the temperature of the methanol-reforming reaction for improvement in energy utilization efficiency, and the overall efficiency in such a case is said to be improved by 31-48%, compared to the case where methanol is directly combusted.
However, when the exhaust gas is used actually for the methanol-reforming reaction, a low-cost longer-lifetime catalyst superior in heat resistance, activity, and abrasion resistance is needed, because the temperature of the exhaust gas fluctuates in the range of 200° C. to 700° C. Base metal elements such as copper, chromium and zinc or the oxide thereof have been generally used as the methanol-reforming catalysts, but although active at low temperature in the reforming reaction for producing water vapor from methanol, these conventional catalysts have a problem of low heat resistance. Alternatively, catalysts of a noble metal element (e.g. platinum) or the oxide thereof supported on a carrier such as alumina are also known, but these catalysts have a problem of high cost.
Under the circumstance surrounding the conventional technology described above, the present inventors paid attention to an intermetallic compound Ni3Al superior in high-temperature properties and abrasion resistance the yield strength of which has a positive dependence on temperature (called reverse temperature dependence of strength) as a methanol-reforming catalyst. The intermetallic compound Ni3Al has been proposed as a molded catalyst (Japanese Patent Application Laid-Open No. 55-88856), but the potential thereof as a methanol-reforming catalyst at high temperature is not studied and there was no report on such applications.